Catalytic steam dealkylation

ABSTRACT

1. A PROCESS FOR CATALYTIC STEAM DEALKYLATION OF ALKYL AROMATIC HYDROCARBON WHICH COMPRISES CAUSING AN ALKYL AROMATIC HYDROCARBON TO CONTACT, IN THE PRESENCE OF STEAM, A CATALYST SUPPORTED BY A CARRIER, SAID CATALYST COMPRISING RHODIUM IN A QUANTITY OF FROM 0.05 TO 5.0 PERCENT BY WEIGHT WITH RESPECT TO THE CARRIER AND AT LEAST ONE OXIDE OF A GROUP IIIB METAL OF THE PERIODIC TABLE IN A QUANTITY OF FROM 0.05 TO 20 PERCENT BY WEIGHT WITH RESPECT TO THE CARRIER.

United States Patent US. Cl. 260-672 R 6 Claims ABSTRACT OF THE DISCLOSURE An alkyl aromatic hydrocarbon is caused to contact, in the presence of steam, a catalyst comprising, as its catalyst ingredients, (1) rhodium, (2) a uranium oxide, and (3) at least one element selected from the group consisting of iron, nickel, cobalt, copper, chromium, and vanadium thereby to accomplish catalytic steam dealkylation of the alkyl aromatic hydrocarbon.

BACKGROUND OF THE INVENTION Field of Art This invention relates generally to dealkylation and more particularly to a process for catalytic steam dealkylation of alkyl aromatic hydrocarbons. More spe cifically, the invention relates to a process for carrying out dealkylation of an alkyl aromatic hydrocarbon oil or a hydrocarbon oil containing an alkyl aromatic by causing the same to contact a novel catalyst having high activity and high selectivity in the presence of steam.

Heretofore, dealkylation of alkyl aromatic hydrocarbon has been carried out on a commercial scale by catalytic and thermal processes in the presence of hydrogen. These dealkylation processes, however, are costly in using large quantities of hydrogen and the unavoidable conversion of the side-chain alkyl groups into lower hydrocarbon gases, principally methane and the like which are merely evaluated as fuel. These economic weak points become more enhanced with increasing number of side-chain alkyl groups, and a process of this nature for dealkylation of higher alkylaromatics other than toluene such as C and C in general, becomes commercially prohibitive or infeasible.

In the steam dealkylation process, inexpensive steam is used instead of hydrogen to carry out dealkylation of alkylaromatic. Accompanied with the production of lower alkylaromatics, generally benzene, a large quantity of high-purity hydrogen can be produced.

The steam dealkylation reaction, in general, may be considered to be a parallel or combined reaction of dealkylation, cracking of a benzene nucleus, and a carbon deposition. For example, in the case where toluene is used as a starting material, a dealkylation reaction as indicated by the following Eq. (1) and a nucleus cracking reaction of the starting toluene or produced benzene as indicated by the following Eq. (2a) or (2b) take place.

The benzene nucleus cracking is a commercially undesirable reaction since it gives rise to a lower yield than contemplated of lower alkylaromatics, generally benzene. Since these two reactions, in general, tend to occur more readily with increasing temperature, the development of a catalyst having high activity in the lower temperature regions and, moreover, functioning to inhibit nucleus cracking reactions is highly desirable.

3,848,014 Patented Nov. 12, 1974 Prior Art Catalysts which have been proposed heretofore as being effective for steam dealkylation reactions can be divided into two classes, in which the principal active components are metallic nickel and a noble metal, respectively. Examples of specific proposals of noble-metal catalysts related to this invention are those of US. Pats. 3,436,433 and 3,436,434 and British Pat. 1,174,879, in which Rhbased catalysts are predominant.

In the specification of British Pat. 1,174,879, there is disclosed that the use of a 0.3% Pt-0.3% Rh-Al O catalyst at 460 C., LHSV 0.5 hrr and toluene: water mole ratio 1:4, leads to toluene conversion 62 mole percent, and selectivity to benzene 92 mole percent. However, this catalyst system and those of the other patents cited above could not be said to be entirely satisfactory. Particularly in cases where noble-metal catalysts are used, the reduction of the content of the expensive noble metals is also one of the principal objects from the standpoint of catalyst price in the development of new catalyst systems.

SUMMARY OF THE INVENTION In view of the foregoing considerations, it is an'object of this invention to provide a process for catalytic steam dealkylation of an alkylaromatic hydrocarbon with high conversion and high selectivity through the use of a catalyst based on Rh-IIIb metal oxide which we have newly discovered.

According to this invention, briefly summarized, there is provided a catalytic dealkylation process as stated above which is characterized by the step of causing an alkyl aromatic hydrocarbon to contact, in the presence of steam, a catalyst comprising rhodium and at least one oxide of a metal of Group filIIb of the Periodic Table.

In accordance with one embodiment of this invention, a high-activity catalyst based on rhodium and a uranium oxide is further improved, particularly with respect to its selectivity, by modifying this basic system with a specific element ingredient.

Accordingly, in accordance with one specific example of this invention, there is provided a process for catalytic dealkylation of alkyl aromatic hydrocarbons which comprises causing an alkyl aromatic hydrocarbon to contact, in the presence of steam, a catalyst comprising (1) rhodium, (2) a uranium oxide, and (3) at least one element selected from the group consisting of iron, nickel cobalt, copper, chromium, and vanadium.

The nature, utility, and further features of this invention will be apparent from the following detailed description beginning with a consideration of general details of the invention and concluding with specific examples of practice illustrating preferred embodiments thereof.

DETAILED DESCRIPTION Catalyst I Composition: The term oxide of a metal of Group IIIb is herein used to designate an oxide of a rare earth element such as yttrium, lanthanum, cerium, and neodymium or of an actinide metal such as thorium and ura nium. We have found that, of the oxides of these elements, those of yttrium, lanthanum, cerium, neodymium, thorium, and uranium are especially suitable for use according to his invention.

The form and state in which rhodium and the Group IIIb metal exist within the catalyst are not fully clear in all cases. While it may be considered that the rhodium exists as the metal and the Group IIIb metal exists as an oxide either independently or with intimate interrelationship, it can also be considered that one portion of the oxide of the Group HIb metal is subjected to a certain degree of reduction in the case of preparation as described below including an oxidation-reduction process step. Furthermore, it may be considered also that a portion of the rhodium is oxidized.

The form and state in which the rhodium (component 1),. uranium oxide (component 2), and iron, nickel, cobalt, copper, chromium, and vanadium (component 3) exist..within the catalyst are also not clear in all cases. However, in the case of a preparation comprising an oxidation-reduction process step as described below, it may be considered that the rhodium is reduced to the metal, the uranium, iron, chromium, and vanadium are reduced to a lower oxide, while the nickel, cobalt, and copper are reduced substantially to the metals.

1 As a customary with this type of catalysts, the rhodium-based catalyst according to this invention is also used ordinarily in a form wherein it is carried on a carrier.

"While the respective quantities of the components may be selected at will provided that the beneficial effect of using together rhodium and the oxide of the Group 1115 metal is exhibited, thefollowing proportions have been found to be generally satisfactory.

The rhodium is used in a carried form in a quantity, as the metal of from 0.05 to 5.0 percent by weight, more practically from 0.1 to 1.5 percent by weight, based on the carrier. The oxide of a Group IIIb metal can be used directly, as it is, as the carrier in this case. In the case, however, where a carrier of generally known porous type such as, for example, alumina, silica-alumina, silica, diato'maceous earth, or nickel aluminate of spinel type is used, quantities of from 0.05 to 20 percent by weight of the carrier of the oxide of a Group III!) metal together with the noble metal are sufficient.

In the desired mode of practice of the invention as described above in the case where the Group IIIb metal is uranium, also, the respective quantities of the compo nents may be selected at will provided that the advantageous effect of using together rhodium and components (2) and (3) is apparent. However, we have found that, in general, the following proportions are satisfactory.

The rhodium is used in a carried form in a quantity as the metal of from 0.05 to 5.0 percent by Weight, more practically from 0.1 to 1.5 percent by Weight of the carrier. While the oxides of uranium, iron, and chromium can be used directly as they are as the carrier in this case, a generally known porous carrier such as alumina, silicaalumina, silica, diatomaceous earth, or crystalline silica or alumina is ordinarily used as the carrier. In this case uranium oxide in a quanity of from 0.05 to 20 percent, preferablyfrom 0.1 to 10 percent by weight of the carrier and the component (2) other than copper in a quantity of from 0.01 to 10 percent, preferably from 0.05 to 5 percent by weight of the carrier are carried on the carrier together with the rhodium, whereby sufiicient effectiveness can be attained.

In the case where copper is used as the component (2), if the ratio of its weight to that of the rhodium is excessively large, the activity of the resulting catalyst will drop abruptly. Therefore, it is desirable that the copper oxide be used in a quantity of from 0.01 to 2 percent, preferably from 0.05 to 1 percent by weight of the carrier.

Catalyst Preparation: While the catalyst preparation can be carried out by any of the appropriate known methods, we have found that the method of introducing soluble compounds of rhodium and the Group IIIb metal from a solution state onto a carrier either simultaneously or in stages is simple and convenient.

For example, 'y-alumina is introduced into a mixed aqueous solution of rhodium chloride and a soluble salt of a Group IIIb metal, and the rhodium component and the salt of the Group IlIb are caused to impregnate the 'y-alumina. After the q -alumina has been thus steeped and impregnated, it is once dried at a tempertaure of from 80 to 100 C. and then dried again for a period of from 1 to hours in an air atmosphere at from 130- to 150 C. Calcination is carried out in air or in an inactive gas at from 300 to 600 C. for a period of from 0.5 to 10 hours. Reduction of the catalyst is carried out in a stream of hydrogen gas or a gas containing hydrogen at from 300 to 600 C. for a period of from 0.5 to 20 hours. The flowrate of the hydrogen gas in this step is generally from 100 to 500 liters/hour per liter of catalyst.

We have found that in the preferred mode of practice of the invention as described above in the case where the Group IIIb metal is uranium, also, the method of introducing the precursor compounds of the components (1), (2), and (3) which are soluble and thermally decomposed into the metal or lower oxide such as for example, nitrates, organic acid salts, and halides, from a solution state onto the carrier either simultaneously or in stages is simple and convenient.

For example, 'y-alumina is introduced into a mixed aqueous solution of rhodium chloride, uranyl nitrate, and n ckel nitrate thereby to impregnate the carrier with the rhodium component, the uranium component, and the nickel component. After the 'y-alumina has been thus steeped and impregnated, it is once dried at a temperature of from to C. and then dried again for a period of from 1 to 10 hours in an air atmosphere at from to C. Calcination is carried out in air or in an inactive gas at from 300 to 700 C. for a period of from 0.5 to 10 hours.

In this connection, in the case where nickel and cobalt are added, particularly in the calcination step, they readily act with the carrier alumina to form a spinel and thereby to render the catalyst inactive, whereby the expected benefit of these additives is nullified. Therefore, it is necessary to limit the calcination temperature strictly within the range of from 300 to 600 C.

The reduction of the catalyst is carried out for a period of from 0.5 to 20 hours in a stream of hydrogen or a gas containing hydrogen gas at a temperature of from 300 to 600 C. The flowrate of the hydrogen gas during this step is generally from 10 to 1,000 liters/hours per liter of the catalyst.

Specific examples of starting-material metal compounds suitable for use in this preparation process are as follows.

Rhodium: Rhodium chloride (hydrate), rhodium nitrate (hydrate), and complex compounds.

Yttrium:

Yttrium bromide Yttrium chloride Yttrium nitrate Yttrium oxide Yttrium carbide, etc.

Lanthanum:

Lanthanum chloride Lanthanum bromide Lanthanum nitrate Lanthanum ammonium nitrate Lanthanum potassium nitrate Lanthanum sodium nitrate, etc.

Cerium:

Cerium oxychloride Cerium tetrachloride Cerium trichloride Ammonium cerous nitrate Potassium cerous nitrate Cerous nitrate Cerous chloride, etc.

Neodyminum:

Neodymium bromide Neodymium chloride Neodymium chloride hexahydrated Neodymium nitrate Neodymium oxychloride, etc.

Thorium:

Thorium ammonium chloride Thorium chloride (hydrated) .Thorium:Continued Thorium potassium hydroxychloride Thorium nitrate (hydrated) Thorium oxychloride, etc.

Uranium:

Uranium nitrates Uranyl acetate Ammonium uranate Uranium oxychlorides Uranyl potassium chloride other uranates Iron, nickel, cobalt, copper, chromium, vanadium nitrates, chlorides, and salts of organic acids (salts of formic acid, acetic acid, and oxalic acid etc.). Modifications: The catalyst according to this invention contains the components (1), (2), and (3) as its essential catalyst components. Within this definitive scope, various modifications are possible, one example of which is the introduction of various metals.

One example of such modification metals is platinum. We have found that a suitable atomic ratio Pt/Rh is in the range of from 0.1 to 10, and that the platinum can be introduced at the aforementioned suitable time of the catalyst in the form of a decomposable platinum compound such as, for example, chloroplatinic acid. The platinum exists principally as the metal.

In addition, alkali metals and alkaline earth metals in the form, for example, of nitrates thereof, and other metals can be introduced.

Steam dealkylation Alkyl aromatic hydrocarbons: Alkyl aromatic hydrocarbons to be used as starting materials in the practice of this invention include: monoalkyl monocyclic aromatics, e.g., toluene, ethylbenzene, and cumene; polyalkyl monocyclic aromatics, e.g., xylenes, ethyltoluenes, and

' trimethylbenzenes; alkyl polycyclic aromatics, e.g., methylnaphthalenes; and alicyclic-aromatics such as tetralin, either singly or as mixtures thereof. For the alkyl group, lower alkyl groups containing from 1 to 6, preferably 1 to 3 carbon atoms are desirable.

In addition, it is also possible to use mixtures of alkyl aromatic hydrocarbons and non-aromatics as, for example, hydrocarbon oil mixtures representable by naphtha cracking bottom oil and catalytic reforming oils which have been subjected to a suitable treatment such as partial hydro-cracking and desulfurization.

Steam dealkylation reaction: Steam dealkylation reaction is generally carried out by thoroughly mixing steam which has been vaporized beforehand by preheating means and an alkyl aromatic hydorcarbon feed oil and then introducing the resulting mixture to a catalyst bed. Variables which should be ,controlled as reaction conditions are the reaction temperature, the reaction pressure, the feedrate, and the'mole ratio of the supplied water and the alkyl aromatic hydrocarbon. In general, these conditions are, respectively, from 300 to 600 C., from atmospheric pressure to 70 kg./cm. from 0.1 to weight/ weight/hour, and from 1 to 30, preferable ranges being,

respectively, from 350 to 550 C., from atmospheric pressure to 50 kg./cm. from 0.3 to 5 weight/weight/ 7 hour, and from 3 to 15.

The tendency of the catalyst activity to progessively decrease increases as the reaction temperature is set at A surface. The catalyst which has thus lost its activity can be reactivated substantially to its initial activity level by introducing thereto a gas containing oxygen at a suitable temperature or by introducing steam thereto.

This carbon deposition can be substantially suppressed by adding an alkali metal and/or alkaline earth metal as a catalyst ingredient as is generally done in steam reforming and, further, by recycling a portion of the gas containing hydrogen which is being formed in the steam dealkylation reaction. If, in resorting to the latter method of suppressing deterioration in catalyst activity, the quantity of the recycled hydrogen gas is large, hydrodealkylation reaction will begin to occur to a considerable extent, whereby not only will the steam dealkylation reaction begin to depart from its true nature, but the concentration of methane within the formed gases will become high, and, unless the separation of hydrogen and methane is considered, the production of hydrogen of high purity will become impossible. Therefore, the mole ratio of the recycled hydrogen gas and the supplied water should be kept below 0.3.

In the case where recycling of hydrogen containing gas is not carried out, a typical composition of the resulting gas is of the order of from 68 to 72 percent of H from 21 to 23 percent of CO from 3 to 6 percent of CO, and from 2 to 7 percent of CH This gas composition indicates that hydrogen gas of high purity can be readily produced with only a C0 absorption column including a CO convertor.

Experiments In order to indicate still more fully the nature and utility of this invention, the following specific examples of practice and results are set forth, it being understood that these examples are presented as illustrative only, and that they are not intended to limit the scope of the invention.

The term selectivity is used in these examplesto designate the proportion, in mole percent, of the feed alkylaromatic nucleus converted into a lower alkylaromatic nucleus without causing nuclear decomposition, that is, the nuclear retention rate. For example, the benzene nuclear retention rate in the case of steam dealkylation of toluene is expressed by the following equation.

Selectivity (nuclear retention rate) rnoles of produced benzene moles of reacted toluene X (mole percent) Example 1 12 ml. of an aqueous solution of rhodium chloride prepared with a concentration of 0.1 gram (g.) of Rh per 20 ml. of aqueous solution is uniformly mixed with an aqueous solution of 0.42 g. of thorium nitrate dissolved in 15 cc. of Water. To the mixed solution thus formed, 20 g. of -alumina, extruded 2 5, is added and the resulting mixture is left standing for 20 hours. After this impregnation step, the 'y-alumina containing the mixed solution is dried for 20 hours in a dryer at 80 C.

The 'y-alumina is then calcined in a stream of air in two stages at C. and 450 C., respectively, each of one hour. After cooling to room temperature, the resulting catalyst is subjected to a reduction process for 2 hours in a stream of hydrogen at 450 C. The theoretical composition of the catalyst thus prepared is, based on the carrier alumina, 0.3 percent Rh-0.5 percent ThO By using 10 g. of the catalyst prepared in the above described manner, steam dealkylation reaction of toluene was carried out in a fixed-bed reactor of ordinary atmospheric-pressure, flow-through type provided with a preheater, and the activity of the catalyst was evaluated under reaction conditions of LHSV of starting toluene of 0.67/hour, reaction temperature of 450 C., and mole ratio of steam to toluene of 6.

From analysis of the product formed in a 2-hour period from 30 minutes to 2 hours and 30 minutes after the start of the reaction, the toluene conversion was found to be 67.3 mole percent, the selectivity to be 98.0 mole percent, and the benzene yield per pass to be 67 mole percent. Furthermore, the composition of the formed gas was found to be 69.9 percent of H 23.8 percent of CO 1.6 percent of CO, and 4.7 percent of CH It was found that by merely removing the CO and CO, a hydrogen gas of sufficiently high purity could be obtained.

7 Example 2 By the catalyst preparation procedure set forth in the preceding Example 1, and through the use of rhodium in a quantity of 0.3 percent by Weight of the carrier alumina and. the use of nitrates respectively of yttrium, lanthanum, cerium, neodymium, and uranium, as the sources of Group IIIb metal oxides, the catalysts indicated in Table 1 were prepared.

The quantity of each Group IIIb metal oxide carried relative to the carrier was adjusted to 0.5 percent by weight in the form of the respective oxide indicated in Table 1 by adjusting the impregnation solution.

The reaction conditions were identical to those of Example 1. The results of this reaction with each catalyst are shown in Table 1.

0.67/hour, and with a weight ratio of the supplied 'wate and the 1,2,4-trimethylbenzene of 1:1. 1

As a result, 1,2,4-trimethylbenzene conversion of 69.5 mole percent, and a selectivity of 96.5 mole percent were obtained. The liquid composition, exclusive of the unreacted trimethylbenzene, was 26.7 mole percent of benzene, 28.5 mole percent of toluene, 3.0 mole percent of p-xylene, 5.4 mole percent of rn-xylene, and 36.4 mole percent of o-xylene. Furthermore, the flowrate-of the formed gas was 8.8 liters/hour, and the gas composition was 71.1 percent of H 23.6 percent of CO 1.9 percent of CO, and 3.4 percent of CH all by volume.

Example 5 7 To 12 ml. of an aqueous solution of rhodium chloride TABLE 1 Mole percent;

Reaction Toluene Benzene temp. eonver- .Qelecyield Number Catalyst composition C.) sion tivlty per pass 450 42.1 see 23:3

2*- 0.37 lib-0.57 Th0 450 67.3 98.0 a. 0.39%, Bil-0.5% Ygog 450 51.2 94.5 48.4 4 0.3% Eli-0.5% 113.103- 150 52. 1 92. 8 48. 3 5 0.3% Ell-0.5% OeOq 450 69.4 91.5 63. 5 6 0.8% Eli-0.5% NdiOa" g8 gilt: 85.2 23% 7 03% Rim-5% U03 Catalyst of Example 1. 7

Catalyst 1 in Table 1 is a catalyst containing only rhoadjusted to a concentration of (0.1 g. Rh)/(20 ml. aquedium without addition of a Group III!) metal oxide and constitutes a comparison example for the purpose of clearly pointing out the purport and utility of this invention. The gas composition corresponding to each catalyst was that indicated in Example 1, and the gas in each case could be rendered into hydrogen gas of sufiiciently high purity by a simple hydrogen purifying step. In the catalyst compositions, the oxidized states of the Group III!) metal oxides have been calculated and added in their forms in Table 1 for the sake of convenience and do not necessarily designate the oxidized states at the time of functioning of the catalysts.

Example 3 By the catalyst preparation procedure set forth in Example 1, a catalyst (catalyst 8) of a composition comprising 0.3 percent Rh-0.75 percent UO Al O was prepared. 10 g. of this catalyst was used to carry out a reaction in the same reactor as that specified in Example 1,

ous solution) and 12 m1. of an aqueous solution of chloroplatinic acid adjusted to a concentration of (0.1 g. Pt)/ (20 ml), 5 g. of an aqueous solution of ura'nyl nitrate made by dissolving uranyl nitrate in a quantity of 0.5 by weight relative to 100 of the carrier alumina thereby to prepare a mixed aqueous solution of rhodium chloride, chloroplatinic acid, and uranyl nitrate. To this mixed aqueous solution, 20 g. of 'y-alumina was added, and the resulting mass was left standing for 20 hours.

Thereafter, this mass was processed by the procedure set forth in Example 1 thereby to prepare a catalyst (catalyst 10) having the composition 0.3% Jib-0.3% Pt0.5%

U0 By using this catalyst, steam dealkylation of toluene was carried out by the process described in Example, whereupon the results indicated in Table 2 wereobtained. Catalyst 9 also shown in Table 2 is a catalyst which was prepared by the same process as that of catalyst What did not contain uranium, and which constituted areference example for the purpose of demonstrating by comwith m-xylene as the feed, at a reaction temperature of parison the utility of this invention.

TABLE 2 Mole percent Reaction Toluene Benzene l iiiih Catalyst composition V ei h per ri s 35:12:12: 312%, filfiii i, ift-strainer: 22 3 53:5 3i? 531i 420 C., at a LHSV of m-xylene of 0.67/hour, and with Example 6 I a weight ratio of m-xylene and supplied water of 1:1.

As a. result, the m-xylene conversion was 76.0 mole percent, the selectivity was 99.5 mole percent, and the conversions to benzene and toluene were 30.4 mole percent and 45.2 mole percent, respectively. Furthermore, the composition of the formed gas was 71.2 percent of H 23.0 percent of CO 2.6 percent of CO, and 3.1 percent of CH all percentages being by volume.

Example 4 10 g. of the catalyst 7 (0.3% Rh0.5% UO Al O described in Example 2 was used to carry out a steam dealkylation reaction of 1,2,4-trimethyl-benzene in the reactor specified in Example 1, at a reaction temperature of Catalyst preparation: 0.78 g. of nickel nitrate is dissolved in 30 cc. of distilled water to form an aqueous solution, to which 20 g. of 'y-alumina (15, extruded) is added, and which is then left standing. for 20' hours. The y-alumina thus steeped in and impregnated with the nickel nitrate is then dried at C. for 20 hours. The y-alumina is further calcined in a stream of air at C. and 450 C. in respective stages of l-hour duration each.

Separately, an aqueous solution of 12 ml. of an aqueous solution of rhodium chloride of a concentration of (0.1 g. Rh)/ (20 ml. aqueous solution) and 0.37 g. of uranyl nitrate dissolved in 15 cc. of distilled water is uni- 420 C., at a LHSV of the 1,2,4-trimethylbenzene of 75 formly mixed. The nickel oxide-alumina previously calcined as described above is added to this mixture, which is then left standing for 20 hours.

A catalyst which had been subjected to the air calcination after the impregnation with rhodium and uranium was calcined in a stream of hydrogen at 450 C. for 2 10 6.44 1iters/hr., and the composition of this gas in mole percent was 71.5 of hydrogen, 24.6 of carbon dioxide, 1.5 of carbon monoxide, and 2.4 of methane.

Thus, the addition of V brings about a definite improvement in the activity of 0.3 Rh-0.5 UO -Al O 5 hours, whereupon a catalyst of a composition 0.3 Rh1.0 We claim: I 3- 2 3 f Converted, was obtalfled- 1. A process for catalytic steam dealkylation of alkyl Steam dealkylatlonreactionz The catalyst thus obtained aromatic hydrocarbon Which comprises causing an alkyl was us ed m a gummy of carry out Steam f aromatic hydrocarbon to contact, in the presence of steam, alkylation reaction of toluene. This reaction was carried 10 a catalyst Supported by a carrier, said catalyst comprising out in an ordinary fixed-bed reactor of atmospher c-pres rhodium in a quantity of from 005 to 50 percent by Sure, flPW'thmugh type under the lieacuon fondltlons of Weight with respect to the carrier and at least one oxide 3 staitmg toluene Y 25 9 8 a mfle/ F 2 of a Group IIIb metal of the Periodic Table in a quantity reactlon temperature 0 an a m0 6 rat) 0 of from 0.05 to 20 percent by weight with respect to the steam to toluene of 6. The activity was evaluated. carrier Results 2. A process as claimed in claim 1 in which the oxide The results of this reaction are showing in Table 3 of Group IIIb metal of the Periodic Table is an oxlde of This Table 3 indicates also the results of reactions under a metal selectd from the group 60518141113 of f i the same conditions as stated above with the use of catalanthanum cenum: P f uramumlysts prepared by the same procedure as set forth above 3 A pro ess as clalmed 1n cla m 1 m which the catathrough the use of iron, cobalt, chromium, and copper y COHtalIlS Platinum a quantlty of from (11 to 10 111 as additive metals other than nickel. terms of the atomic ratlo Pt/Rh.

TABLE 3 Mole percent Tolene Benzene Gas gen- Gas composition (vol. percent) converseleceration Catalyst number Catalyst composition sion tivity (NL/hr.) H4 CO; CO CH4 11--- 0.3 Rh-1.0 UO3-1.0 Ni0 05.7 07.0 5.22 70.0 24.2 1.6 4.2 12.-. 0.3 Rh 1.0 UOs-O 7 F9203 00. 0 04.0 5.40 70. 0 24. 2 2.1 3.7 13-.- 0.3 Bil-1.0 UOa-LO 000. 56.0 95.8 5.01 70.5 24.5 1.4 3.5 14--- 03 Rh-LO 003-10 orzo 68.0 03.1 7.03 70.2 24.0 2.3 3.0 15 0.3 Bil-1.0 U0 -0.2 CuO 54.3 06.2 4.41 68.6 24.1 2.0 5.3 10 0.3 Ian-1.0 U03 58.3 89.8 6.12 69.3 24.8 2 0 3.0

(Converted value with canier alumina as 100 (weight basis).

Catalyst 16 constitutes a reference-example for indicating utility of additives of this invention.

Example 7.To1uene dealkylation reaction with 0.3 Rh0.5 UO (0.52.0)V O A1 O In 27 ml. of deionized water, 0.16 g. of rhodium chloride and 0.37 g. of uranyl nitrate were dissolved to form an aqueous solution, in which 20 g. of 'y-alumina pellets, were steeped and thus left standing for 24 hours. The alumina pellets were thereafter washed thoroughly with deionized water and then dried at 80 C. for 24 hours. Then, in an atmosphere of air in a muffle furnace, the pellets thus dried were fired for one hour at 150 C. and for two hours at 400 C.

The catalyst thus obtained was steeped in 27 ml. of an aqueous solution of ammonium metavanadate, containing 0.26 g. of NH VO and the same procedure as set forth above was followed. 10 g. of the catalyst thus obtained was placed in a. reactor of atmospheric-pressure, flowthrough type and subjected to reduction for 2 hours in a stream of hydrogen of a flowrate of 1.0 liter/ min. and at a reaction temperature of 450 C., whereupon 0.3 Rh-0.5 UO -0.5 V O -A1 O was obtained.

Dealkylation reaction of toluene was carried out under the conditions of a reaction temperature of 420 C., a liquid space velocity of 0.67 cc./cc.-Cat./hr., and a water/ toluene mole ratio of from 5.5 to 6.0 mole/mole. As average values for a reaction time of 8 hours, a toluene conversion of 67.5 mole percent, and a benzene selectivity of 95.1 mole percent were obtained. Furthermore, the average quantity of gas generated during this time was 4. A process for catalytic dealkylation of alkyl aromatic hydrocarbons which comprises causing an alkyl aromatic hydrocarbon to contact a catalyst supported by a carrier said catalyst comprising (1) rhodium in a quantity of from 0.05 to 5.0 percent by weight with respect to the carrier, (2) an uranium oxide in a quantity of from 0.05 to 20 percent by weight with respect to the carrier, and (3) at least one element selected from the group consisting of iron, nickel, cobalt, copper, chromium, and vandium in a quantity of from 0.01 to 10 percent by Weight with respect to the carrier.

5. A process as claimed in claim 4 in which: the rhodium is carried in a quantity, as a metal, of from 0.05 to 5.0 percent by weight with respect to the carrier; the uranium oxide is carried in a quantity of from 0.05 to 20 percent by weight with respect to the carrier; and the oxide of copper is carried in a quantity of from 0.01 to 2 percent by weight with respect to the carrier.

6. A process as claimed in claim 4 in which the catalyst contains platinum in a quantity of from 0.1 to 10 in terms of the atomic ratio Pt/ Rh.

References Cited UNITED STATES PATENTS 3,436,433 4/ 1969 Lester 260 -672 R 3,436,434 4/ 1969 Lester 260672 R 3,595,932 7/1971 Maslyansky et a1. 260672 R CURTIS R. DAVIS, Primary Examiner 

1. A PROCESS FOR CATALYTIC STEAM DEALKYLATION OF ALKYL AROMATIC HYDROCARBON WHICH COMPRISES CAUSING AN ALKYL AROMATIC HYDROCARBON TO CONTACT, IN THE PRESENCE OF STEAM, A CATALYST SUPPORTED BY A CARRIER, SAID CATALYST COMPRISING RHODIUM IN A QUANTITY OF FROM 0.05 TO 5.0 PERCENT BY WEIGHT WITH RESPECT TO THE CARRIER AND AT LEAST ONE OXIDE OF A GROUP IIIB METAL OF THE PERIODIC TABLE IN A QUANTITY OF FROM 0.05 TO 20 PERCENT BY WEIGHT WITH RESPECT TO THE CARRIER. 